Chingford Pond Restoration Project Non-Technical Summary of Environmental Statement West Sussex County Council February 2013
Chingford Pond Restoration Project Non-Technical Summary of Environmental Statement West Sussex County Council Notice This document and its contents have been prepared and are intended solely for West Sussex County Council s information and use in relation to the Chingford Pond Restoration Project. Atkins Ltd assumes no responsibility to any other party in respect of or arising out of or in connection with this document and/or its contents. Document History JOB NUMBER: 5114704 DOCUMENT REF: 1.0 Final for submission H Coutts C McDougall C Hammond A Hughes 28/02/13 Revision Purpose Description Originated Checked Reviewed Authorised Date /Chingford Pond ES_Non Tech Summary
/Chingford Pond ES_Non Tech Summary
Contents Section Page Non Technical Summary 1 Background to the project 1 Description of the proposals 2 Alternative proposals considered 2 Need for Environmental Impact Assessment 3 Consultation 4 Summary of environmental baseline, significant environmental effects and mitigation measures 4 Conclusions 11 /Chingford Pond ES_Non Tech Summary
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Non Technical Summary Background to the project This Environmental Statement (ES) relates to the proposed restoration of Chingford Pond in Burton Park, Sussex. The applicant for the proposal is West Sussex County Council, which previously held a lease on the pond, but in 2012 the pond was returned to the freeholder, Petworth Management Company, which is owned by, and acts on behalf of, the 49 properties in Burton Park. The proposed restoration works involve the raising of water levels in the pond by repairing and raising the existing dam that holds water back to form Chingford Pond. Chingford Pond is one of a series of three ponds (Trout Pond, Chingford Pond and Burton Mill Pond) that were created by building dams on a small stream (referred to in the ES as the Duncton Stream). The general site location is shown on Figure 1-1. The ponds are thought to have been created in the eighteenth century. In 1986 the water levels in Chingford Pond were lowered by approximately 1.5m, by cutting down a section of the existing outflow in the dam. This was done because the volume of water held in the pond meant that it was classed as a reservoir under the Reservoirs Act 1975. A reservoir must be designed to ensure certain levels of safety, and the outflow (spillway) from Chingford Pond did not meet the legal requirements of the Reservoirs Act. Reducing the volume of water in the pond meant that it was no longer classed as a reservoir under the Act. The condition of this outflow worsened in the years after 1986, until eventually it was damaged and partially washed away during a flood in 2001. This meant that the water levels in the pond fell even further, and are now nearly two metres lower than when the dam and pond were originally built. Burton Park and the associated pond system are an environmentally important site. Burton Park lies within the South Downs National Park, and is itself a Grade II Registered Historic Park and Garden. Burton Pond is a designated Site of Special Scientific Interest (SSSI), Chingford Pond is a local Site of Nature Conservation Interest (SNCI) and together the two ponds form the Burton and Chingford Ponds Local Nature Reserve (LNR). The two ponds also support an important and diverse range of plants and animals, and some legally protected species (badgers, dormice) are known to inhabit the woodland areas that fringe the ponds. There are public footpaths that also provide public access to the site. Why is this project being undertaken? Burton Park is a historically important site, being a Registered Historic Park and Garden. Chingford Pond is an important feature within the Historic Park and Garden, and the lowering of the water levels and growth of trees and scrub in the areas that were once extensive open water has meant that the historic landscape has become degraded over time. PMC, working in partnership with a number of other organisations, wishes to restore of a number of historic features within the Park, including Chingford Pond. This is being implemented through PMC s Historic Park Restoration Plan. Chingford Pond forms part of a wider vision for the whole of Burton Park which seeks to restore the park to its previous grandeur of the early 1800s. The vision is to be achieved through the implementation of a Historic Park Restoration Plan. Chingford Pond forms part of this Restoration Plan and the proposed scheme seeks to restore the pond as a fundamental part within the historic landscape. The project is supported by Natural England and as such PMC have been awarded funding through the Countryside Stewardship Scheme to deliver its objectives Additionally, there is an existing planning condition (a Section 106 agreement) relating to the previous development of residential housing at Burton Park, which requires PMC to undertake the restoration of Chingford Pond. /Chingford Pond ES_Non Tech Summary 1
Additionally, although the reservoir is not currently within the Reservoirs Act, 1975, its condition has deteriorated over time and so works are required to make it safer. In addition the reservoir may come under the ambit of the Flood and Water Management Act, 2010, when implemented. Description of the proposals The proposed works to Chingford Pond aim to restore the water level in the pond to the level it was at before the pond was first lowered in 1986 (the historic level). This will involve: Repairing and restoring a historic rock-faced cascade (which gives the appearance of a waterfall). This used to be the place where water flowed out of the pond and through the dam into Burton Mill Pond; Repairs to the dam, including filling in some areas on the top of the dam, to ensure that it is at an even height all along its length. This will ensure that water is retained at the intended level, especially during a flood. Returning the water to its original level in the pond will mean that it is once again classed as a reservoir under the Reservoirs Act, 1975, and must meet the legal safety requirements of the Act. This mainly relates to ensuring that if a flood occurs and the reservoir is able to safely pass the required design flood event flows. In order to do this, two new reinforced spillways need to be built into the dam. These structures are specifically designed to carry flood water safely over the dam and into Burton Pond. These spillways will only have water flowing down them once the pond has filled up to a certain level during a flood. At all other times they will be dry. Two spillways are required to account for different levels of flooding; the first spillway will be smaller and will carry away smaller amounts of floodwater. The larger spillway is designed only to be used in very extreme flood events, and it is expected that it will only be working on very rare occasions. In addition to these new spillways, a footbridge just to the north of the dam will be replaced, and some reinforcement works will be carried out to a stream bank which is eroding. In order to undertake the works, a number of large trees will need to be removed from the construction area around the dam. Trees and other vegetation will also need to be removed from the area around the edge of Chingford Pond, otherwise they will die and rot away after they are flooded by the newly raised water levels. The construction works to repair the cascade and build the new spillways are anticipated to start in June 2013, and will be completed by November 2013. However in order to protect the important plants and animals that currently live in Chingford Pond the actual raising of the water levels will take place very slowly and gradually, over a period of up to 10 years after construction has finished. Alternative proposals considered The proposals for Chingford Pond have been in development for a number of years. Five options to repair the damage to the dam and reinstate different water levels in Chingford Pond were considered during earlier phases of work. These options were: Full restoration of Chingford Pond to its historic water level (approximately 2m higher than it is now); Partial restoration of the pond to a middle level, approximately 1m higher than the water is now; Returning water levels to where they were when the dam was first lowered in 1986, approximately half a metre higher than they are now; Repair the damage to the dam and keep the water levels where they are today; and /Chingford Pond ES_Non Tech Summary 2
Do nothing (undertake no work at all) The engineering (technical) and environmental issues associated with each of the alternative options were considered. In the end the full restoration option was chosen as it was considered to be the only way to meet the objectives for the historic restoration of the pond. It was recognised that there would be some implications for the other environmental features of the pond, and that these would need to be appropriately dealt with to ensure that the wider environment was protected. Alongside the water level raising options, it was also investigated whether it would be possible to remove sediment from the ponds that has built up over the years, and which has reduced the depth of the water considerably. There was found to be a good deal of sediment build up within the ponds, and it would not be cost effective to try and remove it. Need for Environmental Impact Assessment Certain types of development proposals that exceed a specified size, and which may have a significant impact on the natural or human environment are required by law to undergo an Environmental Impact Assessment (EIA). EIA is a process which examines and reports on the potential implications of a development on the environment (both beneficial and ), and seeks to find ways to overcome any effects that are identified. It is up to local planning authorities (in this case Chichester District Council and the South Downs National Park Authority) to decide whether or not a development will need an EIA. West Sussex County Council requested that the need for an EIA be confirmed, and if one was required, confirmation of what environmental issues should be considered in the assessment. Chichester District Council confirmed that, given the size of the proposals and the environmental sensitivity of Chingford Pond and Burton Park, an EIA should be carried out. The Council and South Downs National Park Authority also advised that the key issues that need to be considered in the EIA were: The ecological effects of the proposals, including the effects on Burton Pond SSSI, Chingford Pond SNCI and Burton and Chingford Ponds (LNR); Consideration of positive impacts on Burton Mill Pond SSSI due to reduced sediment inputs from Chingford Pond following the repair of the dam; Impacts on protected species in the area (bats, badgers, dormice, water voles and reptiles) Impacts on the flora and fauna that currently use Chingford Pond, especially the stands of aquatic plants that are established around the edge of the pond, and one particularly important snail, Desmoulin s whorl snail, which lives in this habitat; The effects on other aquatic species and habitats from a reduction in the area of shallow water and marginal habitats and an associated increase in deeper open water habitats in the pond; The implications of habitat losses due to water level raising from the Duncton Stream (the inflow to Chingford Pond) and the two areas of woodland that have developed to the south of Chingford Pond since it has dried out; Opportunities for ecological improvements for protected species or other habitats at the site; and Impacts of the scheme on the water quality of the pond system, both during the construction works and once the water levels are raised. These and a range of other environmental issues such as impacts on local residents, impacts on landscape and the potential for noise generation during the construction works have also been considered in the EIA. /Chingford Pond ES_Non Tech Summary 3
Consultation Consultation is an important aspect of the EIA process, and is necessary not only to help define the scope of the EIA, but also to help develop and refine the details of the proposed scheme, identify any required changes to the design that may be needed or develop measures that are needed to protect the environment. Three rounds of consultation have been undertaken during the early stages of the EIA process. Initially this was limited to regulatory and advisory bodies such as the local Councils, the Environment Agency, English Heritage and Natural England. Other local interest groups have also been consulted throughout the development of the project, particularly Sussex Wildlife Trust, which manages the LNR, and the associated LNR Committee. West Sussex County Council also organised a public exhibition on 24th October 2012, for local residents and other stakeholders to gain an understanding of and make comments on the proposals for the restoration of Chingford Pond. There were approximately 30 attendees, including local residents from Burton House. The proposed plans were generally well received with no objections being raised. When the planning application is submitted, this ES will be circulated to the relevant consultees by the planning authority, and will be made publically available on the planning authority s website. Responses to the consultation on the application and this ES will be taken into account in determining the planning application and any required planning conditions. Summary of environmental baseline, significant environmental effects and mitigation measures In this section, the key environmental features of the area that could be affected by the proposals at Chingford Pond are briefly summarised. There then follows a table that summarises the main environmental impacts that have been identified by the EIA proposals, and the measures that will be used to address them (if required). Community/Social The key community/social baseline features are: The residential properties in Burton Park located to the north of Chingford Pond within 50m of the proposed site compound and haul routes, including houses at Lodge Green and residential properties at Burton House; Burton and Chingford Ponds are a designated Local Nature Reserve, which is open to the public all year round. There is an easy access nature trail through the Reserve, part of which runs over the dam; and The site can currently only be accessed by a public right of way to the eastern edge of Chingford Pond, crossing the culverts and cascade feature across to the farmland beyond. A bridleway crosses between Chingford and Trout Ponds to the west and these connect to a network of public footpaths within Burton Park. These also form part of two long distance walking trails: the West Sussex Literary Trail and the Serpent Way. The remainder of the site is owned by the residents of Burton Park and is not accessible to the public. /Chingford Pond ES_Non Tech Summary 4
Environmental Receptor Description of Impact Further Mitigation or Action Required Residual Impact Summary of Impacts During Construction Local residents Cumulative impacts of nuisance caused by increased dust, noise and visual impacts. Dust to be controlled by good working practices on site, as set out in the EAP. Best practice measures as identified specifically for noise and visual impacts. Recreational use of the site, LNR and footpaths in the wider area. Temporary loss of access due to footpath closures. Walkers using the Long Distance Walking Trails will need to seek alternative routes, which could increase the distance to be covered on the LDWTs. Reductions in continuity of access at LNR, reduction in tranquillity if construction noise is audible. Route closures have been agreed in principle with the West Sussex County Council Rights of Way department. The need for route closures will be advertised in advance of the works, but this will not reduce the overall magnitude of effect. Noise will be controlled by good practice measures as detailed below. All identified impacts are short term, temporary and immediately reversible on completion of construction. Moderate Summary of Impacts During Operation Recreational users of the site Long term in-combination effect of new spillways and vegetation removal () followed by a long term improvement in amenity from raised water levels (beneficial) The spillways have been designed to blend in to the area as far as possible, but there will still be some effects. On balance the beneficial effects should outweigh the. beneficial Terrestrial Ecology The terrestrial ecology of the area immediately surrounding Chingford Pond has been investigated in some detail during the development of the proposals. The habitats and species found within Burton Park (including Burton Mill Pond) are considered to be nationally important, and some of Burton Park has therefore been designated as a SSSI. There are also several other sites nearby (including Chingford Pond) which are recognised as being of local importance for nature conservation, and are therefore designated as SNCIs. Chingford Pond is bordered by areas of woodland. This includes important ancient and wet woodland habitat types. Some patches of the woodland have been colonised by undesirable invasive species such as Japanese knotweed and rhododendrons. The following legally protected species have been recorded during surveys of the site, and will require special consideration and management before, during and after the works: Dormice (in the woodlands to the south of the pond); Badgers (three badger setts have been recorded in the woodland areas surrounding the pond); Bats (recorded feeding over the pond area, hibernating in a tunnel in front of the cascade, and may also be using mature woodland trees as roost sites); and It is considered likely that reptiles will be present in the terrestrial habitats surrounding the ponds. No water voles, otters or great crested newts have been recorded at the site during specific ecological surveys to check for these species. The habitats around Chingford Pond also support a diverse range of terrestrial invertebrate species. /Chingford Pond ES_Non Tech Summary 5
Environmental Receptor Description of Impact Further Mitigation or Action Required Residual Impact Summary of Impacts During Construction Wet Woodland Direct loss of 3.4ha of young, poor quality wet woodland habitat The establishment in time of an area of wet woodland habitat to the north of the estate. Positive Bats Potential loss of trees with bat roost potential on the local bat assemblage. Tree roosts: Surveys prior to work commencing. The mitigation for tree roosts will be in three phases: 1) the timing of the felling of trees with bats/bat potential; 2) the provision of alternative roost areas for bats and 3) the recreation of foraging habitat for bats. Grotto: The amount of fill required should allow the grotto to be maintained as a bat hibernation site. Securing the grotto with a lockable grilled gate will reduce disturbance by human activity during the key hibernation season but maintain access for bats. The grotto mitigation will be in two phases; 1) the timing of the works and 2) the provision of an alternative roost site and enhancements to the new grotto. Moderate Adverse Dormice Dormice have been recorded in areas of sub-optimal and optimal habitat, however, it is considered likely that the species occurs, albeit at lower densities, in the other wooded habitats within the site. The loss of these woodland habitats would have an impact on the local dormouse population. Four main principles for mitigation are proposed to provide beforehand a more than satisfactory replacement habitat to maintain the population of the species as they are considered as a favourable conservation status and in their natural range: Habitat enhancement of Half Moon Copse; Habitat enhancement of southern boundary be planting of 600m2 along the southern boundary of the site which is currently been cut back for arable field; Habitat creation Timings of vegetation clearance Method of vegetation clearance Moderate Positive Harvest Mouse A single harvest mouse nest was found in emergent vegetation at the western end of Chingford pond during the water vole and otter survey. The western end of the pond will not be directly affected by the proposals. No specific mitigation for harvest mice is proposed. Habitats will remain within the site which are suitable for harvest mice. Adverse Breeding Birds Loss of bird habitat across the site The initial clearance works of woodland habitat is considered to be the most significant impact on breeding birds, however, it will be undertaken at a time of year that will minimise these impacts. The final outcome of the scheme will create a diverse range of habitats and where additional planting has been recommended for dormice the species Benefit /Chingford Pond ES_Non Tech Summary 6
Environmental Receptor Description of Impact Further Mitigation or Action Required Residual Impact suggested will also benefit breeding birds. Overall Biodiversity Loss of habitats associated with entire works The initial impacts of clear felling woodland areas will have an effect on a locally important habitat that if undertaken at the wrong time of year could have a serious detrimental impact on certain wildlife groups. However the mitigation and long-term restoration proposals to create wet woodland habitats and enhance areas for dormice and breeding birds will result in a long term ecologically beneficial effect. Benefit Summary of Impacts During Operation Terrestrial Invertebrates Due to the habitats found on site a number of rare and uncommon terrestrial invertebrates have been recorded. The loss of the marginal habitat such as fen, swamp and wet woodland is considered to be the most detrimental impact on terrestrial invertebrates. With regard to fen and swamp habitats, however, the raising of the water level from 16.5m to 18.3m at 0.20m a year is considered to be slow enough to allow the plant species associated with these communities to migrate. The final outcome of the scheme will result in a mix of marginal and woodland habitat. The creation of fen and swamp habitat will bring these habitats closer to well established tree line and woodland edge. This would bring the shallow margin under tree canopy that will increase the amount of shading than at present levels. To reduce this impact would mean that trees along the pond margin would need to be selectively thinned or coppiced. Benefit Landscape and Visual Burton Park is set within the South Downs National Park. At a more local level, Burton Park and the surrounding area have a high sense of tranquillity, due to the absence of noticeable road infrastructure, surrounding agricultural land use, woodland cover and enclosure from the field patterns and vegetation. The landscape is considered to be highly sensitive to change at a regional and local level. The site itself (for the purposes of the landscape assessment this is defined as Chingford Pond and the adjoining woodlands to the south) is part of a designed historic landscape and is a key element of Burton Park. However the damage to the dam and the vegetation that has overgrown the pond area since the water levels have dropped have negatively affected this designed landscape, and as a result it is considered to have a medium rather than high sensitivity to change. Burton Park has a number of individual mature and very mature trees within a parkland setting. There are managed hedgerows and more formal gardens. The vegetation around Chingford Pond is a mixture between mature woodland such as oak, growing in narrow sections along the southern and northern boundaries, and areas of self set trees such as alder and goat willow. The areas of alder and goat willow are predominantly in the areas between the former pond edge (when water levels were higher) and the current low water level. This vegetation screens the visual links between the pond and the parkland, including Burton House. Key viewpoints and visual receptors within the study area were deemed to be Burton House, the properties at Lodge Green, and walkers using the public rights of way that pass over the dam and at the far western end of Chingford Pond. /Chingford Pond ES_Non Tech Summary 7
Environmental Receptor Description of Impact Further Mitigation or Action Required Residual Impact Summary of Impacts During Construction Landscape character at the site level (defined as Chingford Pond and adjoining woodlands) A localised, perceptible change due to the presence of the construction works. Good practice measures on site during construction to minimise the extent of the works and associated impacts. Vegetation between existing and proposed water level, and on northern bank at the location of the proposed view corridor Loss of vegetation due to required clearance for water level raising and view enhancement. Mainly self-set vegetation but some oaks in view corridor. Retention of alders along final water line where feasible. Within view corridor, retain important oaks as individual trees. Vegetation around the dam and at the cascade / grotto Loss of vegetation, including mature trees such as beech and oak due to required clearance for construction. None available as clearance is required for engineering and operational reasons Moderate Residents of Burton House and Lodge Green with views of works, users of public right of way at western end of Chingford Pond, and views from Burton Park Road Impacts on views due to the presence of the construction works. Generally the scale of impact is small within the context of the wider setting. Good practice measures to minimise the extent of the works. Summary of Impacts During Operation Landscape character at the site level (defined as Chingford Pond and adjoining woodlands) Effects of the repair of the breach, restoration of the cascade / grotto, and re-establishment of view connections with Burton House. None required beneficial Woodland areas at Heron Wood Treatment of invasive species proposed as part of works None required beneficial Vegetation between existing and proposed water level, and on northern bank at the location of the proposed view corridor No re-establishment of self-set vegetation within these areas due to water level raising, thus retaining the re-established view corridors with Burton House. None required beneficial Vegetation around the dam and at the cascade / grotto No re-establishment of mature trees and vegetation within these areas permitted to protect integrity of dam and new structures. None available Moderate Residents of Burton House and Lodge Green with views of Chingford Pond, users of two public rights of way (at western end of Chingford Pond and between Heron Wood and Burton House), views from Burton Park Road Re-establishment of open views of Chingford Pond. Screening of new spillway structures by existing vegetation. None required beneficial Users of public right of way between Burton Park and Crouch Farm (over the dam) New spillways and dam would be noticeable changes in the view, but only a small extent of the footpath is affected. None available /Chingford Pond ES_Non Tech Summary 8
Noise Ambient noise levels in Burton Park are relatively low. A noise survey was undertaken at Lodge Green and Burton House, and recorded that background noise in the area was dominated by local birdsong, with occasional distant overhead air-traffic and distant road traffic noise from the A285 faintly audible. Environmental Receptor Description of Impact Further Mitigation or Action Required Residual Impact Summary of Impacts During Construction Two properties at Lodge Green; Downlands and Westfield Lodge Plant noise from construction site. Good practice measures including setting defined working hours, keeping local residents informed of the construction progress and programme. Acoustic screening if required to reduce noise levels to below the BS5228 Category A threshold of 65dB, therefore no longer resulting in a significant impact.. Targeted consultation with the owner/occupier of the nearest household will also be specifically undertaken. Adverse Water Environment The key elements of the water environment within the study area are as follows: The designation of Burton Mill Pond as part of the wider Burton Park SSSI, and the designation of Chingford Pond as a local SNCI, in recognition of the nature conservation value of the existing pond habitats; The water quality of the Duncton Stream, Chingford Pond and Burton Mill Pond has not been directly sampled and tested, but the numbers and diversity of aquatic invertebrates found living in the stream and ponds during ecological surveys indicate that the water quality is high; Chingford Pond supports some important aquatic habitats, including the open water of the pond itself, but of particular importance are the extensive stands of reeds and other water plants that grow at the very edges of the pond where the water is shallower. The Duncton Stream which flows into and out of Chingford Pond also contains a good variety of stream habitat types; Chingford Pond, Burton Pond and the Duncton Stream have all been found to contain a rich and diverse range of aquatic invertebrates, including some locally and nationally rare species. One species of particular importance is Desmoulin s whorl snail, a very small snail that depends on the stands of reeds and other water plants in the shallow margins of the pond. Populations of this snail have been declining across Europe and nationally in the UK. Chingford Pond and Burton Mill Pond are particularly important because they have some of the highest recorded densities of Desmoulin s whorl snail in the whole country; and Some important species of fish have also been recorded in the Duncton Stream and the pond system, including bullhead and European eels. /Chingford Pond ES_Non Tech Summary 9
Environmental Receptor Description of Impact Further Mitigation or Action Required Residual Impact Summary of Impacts During Construction Water quality (secondary receptors include aquatic ecology and SSSI/SNCI designations) Risk of reduction in water quality from pollution risk due to presence of construction works (leaks, spills, runoff, sediment disturbance and dewatering operations) Construction planning, site set up and working methods to be in line with relevant best practice pollution prevention guidance. Specific working methods to be developed for activities within channels or directly over water. Fen vegetation near existing breach in dam Direct loss of a small area of fen vegetation due to temporary cofferdam and installation of scour pipe. No definite measures available some floating fen vegetation could be moved away from the area but the success of this is uncertain. Summary of Impacts During Operation Burton Mill Pond SSSI Reduction in rates of sediment input to the SSSI due to repair of breach and raising of water levels in Chingford Pond. This may reduce the reported rate of loss of open water in Burton Mill Pond. None required beneficial Chingford Pond SNCI Increase in area of open water may be beneficial for some species of overwintering birds that use the site. None required beneficial Fen habitats at head of Burton Mill Pond that formerly supported populations of Desmoulin s whorl snail Re-wetting of some of the upper parts of the area in the long term due to flows being redirected through the cascade when final water level is reached. None required beneficial Open water habitats in Chingford Pond Increase in area of open water habitats (albeit of lower ecological value than shallower and marginal areas). None required beneficial Stream habitats Long term permanent loss of locally important stream habitats from the Duncton Stream between Trout and Chingford Ponds (400m) due to inundation, and loss of Duncton Stream between Chingford and Burton Mill Pond (60m) due to drying out when flows are redirected down the cascade. None identified Gradual raising of water levels at rate of no more than 0.2m per year, to allow habitats to migrate slowly backwards as far as gradient/topography of margins allows. Undertake water level raising in winter, outside of active growing season of wetland plants. Regionally important population of Desmoulin s whorl snail in Chingford Pond Potential loss of extent and diversity of marginal (fen and swamp) habitats on which this species is dependent. Clearance of trees at head of Chingford Pond in the long term to create space for new fen habitats to develop. Clearance of encroaching trees at head of Burton Mill Pond to reduce shading of this area. Close monitoring of pond levels, particularly following high rainfall events, and prompt adjustment of scour pipe control valve in order to maintain water levels at the required level. Not all of the environmental factors that influence the health and survival of this species are fully understood, and the effectiveness of the proposed mitigation cannot be guaranteed at this stage. Uncertain /Chingford Pond ES_Non Tech Summary 10
Environmental Receptor Description of Impact Further Mitigation or Action Required Residual Impact Annual monitoring of this species is required to determine the ongoing effects of the water level raising and the effectiveness of the mitigation. If mitigation is not effective, water levels may need to be held until an alternative mitigation solution is agreed and implemented. Assemblages of aquatic invertebrates of high and very high conservation value in Chingford Pond and the Duncton Stream. Adverse impacts of habitat changes in Chingford Pond due to loss of shallower areas and margins and increase in deep open water. Loss of the stream habitats from Duncton Stream which also support rich and diverse aquatic invertebrates, including rare/scarce species. The mitigation measures described for Desmoulin s whorl snail above are also intended to avoid impacts on the aquatic macroinvertebrate assemblages in Chingford Pond. No mitigation has been identified for the loss of aquatic macroinvertebrate assemblages from the Duncton Stream (upstream and downstream of Chingford Pond). Moderate Impacts on eel passage into Chingford Pond and upstream The repair of the breach could impair or reduce the ability of eels to migrate upstream through the pond system. An eel pass has been proposed and will be installed in the cascade. However as the cascade will not be operational for approximately 10 years, there will be an intervening period where eel passage is potentially impaired or reduced. (mediumlong term) Negligible (long term) Bullhead population in Duncton Stream upstream of Chingford Pond Inundation of stream habitats and eventual loss of this population Capture and translocation of existing population to a suitable receptor site downstream of the works (to be confirmed by surveys in September 2013). No mitigation identified for overall loss of bullhead habitat (and therefore the population) in this area Conclusions The restoration of historic water level at Chingford Pond is proposed with the principle aim of enhancing Chingford Pond as a significant historic asset within Burton Park. The initial lowering of the water level in 1986, followed by the subsequent breaching of the outflow structure in 2001 has resulted in the degradation in quality of the designed landscape within the context of the Historic Park and Garden. Previous phases of work relating to this scheme have identified that the proposed scheme is the most suitable option to reverse this. The EIA process has identified that significant environmental effects will arise as a result of the construction and operation of the development. Of the 17 effects, 11 occur during construction and are therefore temporary in their nature. The 32 significant effects range in level of significance from moderate to moderate beneficial. Five of these effects will be of moderate significance, 12 of these effects will be of minor significance, 13 of minor beneficial significance and one of moderate beneficial. No effects of major significance, have been identified. The effect on the Regionally important population of Desmoulin s whorl snail in Chingford Pond at this stage is uncertain. The temporary minor effects identified in the ES are associated with construction impacts on local residents during the construction period from noise, temporary changes to local landscape character during construction and impacts on visual amenity for residential receptors until the works are completed. Four permanent minor impacts arise because of minor changes in view from the footpath of the new works, loss of stream habitats, impacts on eel passage (medium term), and potentially on the bullhead population. /Chingford Pond ES_Non Tech Summary 11
Ten other minor beneficial operational impacts were identified; which relate to improvements in landscape character, re establishment of views to local residents, recreation and improvements in vegetation. There is also a potential minor beneficial effect on the Burton Mill Pond SSSI due to the reduction of the perceived impact of continuous sediment input through the pond systems. Two permanent effects of moderate significance were identified during operation. These are: Visual impacts associated with tree/vegetation removal around the dam and at the cascade and grotto; and The long term loss of assemblages of aquatic invertebrates of high and very high conservation value, particularly in the Duncton Stream. The majority of the other identified effects will be addressed through standard good construction practice, as described in the accompanying Construction Environmental Management Plan (CEMP). Additional mitigation and compensation measures have been identified as being necessary during the construction and operational phases of the scheme. These will be implemented either by a planning agreement tied to the planning permission or conditions attached to the permission, and/or by the CEMP, which will be used to ensure that environmental issues are addressed and mitigation measures identified in the ES are put in place. It is considered that provided the identified good practice measures are followed, the mitigation and compensation measures are secured and in place, and the recommended monitoring and ongoing management of the water level raising is implemented, the restoration for the benefit of the Historic Park and Garden can be constructed and operated without having a detrimental effect on the wider environment of Chingford Pond. /Chingford Pond ES_Non Tech Summary 12
Heather Coutts Atkins Woodcote Grove Ashley Road Epsom Surrey KT18 5BW heather.coutts@atkinsglobal.com Atkins Ltd except where stated otherwise. The Atkins logo, Carbon Critical Design and the strapline Plan Design Enable are trademarks of Atkins Ltd.